EXHAUST GAS PURIFYING DEVICE FOR INTERNAL COMBUSTION ENGINE

PURPOSE:To prevent pollution of an adsorbent and the occurrence of thermal deterioration by branching a bypass passage, in which an adsorbent is located, from an exhaust gas passage situated downstream from a muffler, detecting the adsorbing condition of hydrocarbon from an engine operation state, and switching the bypass passage and the exhaust gas passage based on the detected result. CONSTITUTION:Exhaust gas from an engine 1 is guided to a muffler 8 through exhaust gas pipes 7a and 7b in which three-dimensional catalysts 9a and 9b for purifying exhaust gas are located. A bypass passage 23 which is branched in a position, situated downward from a muffler 8, from an exhaust gas main passage 22 and in which an adsorbent 24 is located is provided. A switch valve 25 is arranged in a position situated upper stream from the adsorbent 24 and a purge passage 26 is located between the adsorbent 24 and the switching valve 25. HC eliminated from the adsorbent 24 is inputted to a position situated downstream from a throttle valve 3 through a purge passage 21. The operation state of an engine is decided by a control unit 10 by means of signals from various sensors to switch a switching valve 25 into a state to open the bypass passage 23. Performance of the adsorbent 24 is prevented from deterioration in a way that exhaust gas after removal of unburnt oil and carbon by means of the muffler 8 is caused to pass therethrough.